256 Messrs. Allen and Pepys on the Changes produced in 
Calculation for Carbonic Acid. 
100 : 8.5 : : 3437 : 292.145. 
So that 292.14 cubic inches of carbonic acid gas were given 
off in eleven minutes, or 26.55 cubic inches per minute, which 
is almost exactly the estimate of Professor Davy. 
In this experiment the operator inspired 3460 cubic inches 
in eleven minutes, and felt himself in a natural state when he 
left off. Then, as he makes usually under common circum- 
stances nineteen respirations in a minute, 
11 x 19 = 209 = 16.5 
it follows, that he takes in 1 6\ cubic inches at every easy in- 
spiration. 
As all the experiments had been hitherto made upon the 
lungs of one person, we concluded that the next should be per- 
formed upon our assistant. 
Barom. 
Therm. 
Faht. 
3°-3 56 ° 
Twelfth Experiment. 
Time. 
5| min. 
Cub. inches of 
common air 
Inspired. 
33 °° 
Cubic Inches 
Expired. 
33 11 
Difference. 
11 increase 
Here, as usual, the lungs were exhausted both before, and at 
the close of the experiment. 
The excess of eleven cubic inches, in this case, no doubt 
arose from the person not having been in the habit of ex- 
hausting his lungs, so that they contained more when he 
began than when he left off ; his lungs appeared to be of 
greater capacity than those of the usual operator. 
Portions of gas were saved from each of the mercurial 
